The present invention relates to a solid-state image pickup device, a solid-state image pickup device equipped with an optical lens (called as a camera module in the following description) and its manufacturing method.
The construction of a conventional camera module using such a solid-state image pickup device as a CCD image sensor, CMOS image sensor or the like will be described with reference to FIG. 1A and FIG. 1B. FIG. 1A is a perspective view of a camera module and FIG. 1B is its vertical cross-sectional view. As illustrated in these figures, a lens holder 1 is fixed stationary on a printed circuit board 2. The lens holder 1 is made of cylindrical section 1-1 and a square cylindrical section 1-2 that has a larger horizontal sectional area than the horizontal sectional area of this cylindrical section 1-1. On the side surface of the printed circuit board 2, electrode sections 3 are formed for an external connection. Inside of the cylindrical section 1-1 of the lens holder 1, a lens barrel 4 is inserted. The lens barrel 4 is screwed in the cylindrical section. That is, the outer periphery of the lens barrel 4 is threaded (not illustrated) and the inner periphery of the cylindrical section 1-1 of the lens holder 1 is threaded to engage with the thread of the lens barrel 4. Accordingly, the lens barrel 4 is moved vertically when the lens barrel 4 is rotated in the clockwise or counterclockwise direction in the cylindrical section 1-1 of the lens bolder 1. On the printed circuit board 2, a passive part 5 such as resistor, capacitor, etc. and a solid-state image sensor 6 are mounted. An electrode (not shown) of the solid-state image device 6 is connected to an electrode (not shown) of the printed circuit board by a bonding wire 7. The solid-state image sensor 6 is further connected to the passive part 5 (not shown). The printed circuit board 2 is connected to outside parts (not shown) through its electrode section 3. Passive part 5 is connected to a wiring section (not shown) of the circuit board normally by the ref low soldering. The reflow soldered section is shown by 5′.
In the lens holder 1, an optical filter 8 such as an infrared rays cutting filter is joined to the lens holder by a bonding agent 9. Inside of the lens barrel 4, an optical lens 10 is fixed. The lens barrel 4 is adjusted and fixed at a prescribed height in the cylindrical section 1-1 of the lens holder 1 by a screw. At the position of this prescribed height, an image taken by the optical lens 10 is formed on the sensing section (not shown) of the solid-state image sensor 6.
A method for manufacturing parts in the conventional camera module shown in FIG. 1A and FIG. 1B will be explained using FIG. 2 through FIG. 6. In the following description, the same elements as those shown in FIG. 1A and FIG. 1B are assigned with the same reference numerals. In the cylindrical lens barrel 4 shown in FIG. 2(a), the optical lens 10 is fixed as shown in FIG. 2(b). In the square cylindrical portion 1-2 of the lens holder 1 shown in FIG. 3(a), an optical filter 8 is fixed by a bonding agent and then, the lens barrel 4 is screwed in the lens holder 1 as shown in FIG. 3 (c).
FIG. 4 (a) through FIG. 4(e) show the module assembling processes. The passive part 5 is formed on the printed circuit board 2 (FIG. 4(a)) according to the reflow soldering method (FIG. 4(b)). After bonding the solid-state image sensor 6 on the printed circuit board 2, it is connect on the printed circuit board by a bonding wire 7 (FIG. 4(c). Next, the lens holder 1 that was assembled as shown in FIG. 3 is bonded and fixed on the printed circuit board 2. Then, an image taken by the lens 10 is fixed at the position of image forming height of the solid-state image sensor. A camera module is thus formed (FIG. 4(e)).
Next, FIG. 5(a) through FIG. 5(e) show the cutting process of solid image pickup chips from a wafer of which semiconductor manufacturing process was completed. On a wafer 11 of which semiconductor manufacturing process was completed, a solid-state image sensor is formed on each of several chip areas 6′ in the same area (FIG. 5(a)). The solid-state image sensor 6 is separated to respective chips by dicing the sensors 6′ along the boundary lines 6″ which divide respective chip areas 6′. Normally, prior to this dicing process, the electrical and optical tests of each solid-state image pickup chip are conducted (hereinafter, this is called as the wafer test) and an identification mark that is called as the bad mark (not shown) is attached to defective ships. At the center of the solid-state image sensor, a photosensitive area 13 in which pixels are arranged in a matrix is formed and a bonding pad 12 is arranged on the peripheral part of the chip (FIG. 5(b)). FIG. 5(c) shows the cross-section cut along a arrow line AA′ of FIG. 5(b). As shown in FIG. 5(c), plural micro-lenses 14 are formed on the surface of the photosensitive area 11 at the center of the solid-state image sensor 6 corresponding to respective pixels. The micro-lenses 14 promote the sensitivity of the solid-state image sensor by increasing the focusing property to pixels of the solid-state image sensor.
In the conventional camera module manufacturing process, such problems as described below are normally generated.
1) As shown in FIG. 1B, since the passive part 5 is formed on the same printed circuit board 2 with the solid image sensor 6 in the camera module, the module size becomes inevitably larger than the size of the solid-state image sensor. This will be disadvantageous for the downsizing of modules.
2) As shown in FIG. 1B, several units of capacitor of 0.1 uF are needed as a passive part 5 for a camera module. For an ordinary capacitor of this capacity, its external dimension is 0.6×0.3×0.3 mm (called as 0603). In the case of ceramic capacitor in further small size 0.4×0.2×0.2 mm (called as 0603), its capacity is about 0.01 uF at present and therefore, number of capacitors arranged on a circuit board increases and module size becomes larger than the size using 0603 size ceramic capacitors.
Further, when capacitors are mounted on the surface of the circuit board 2 by the reflow soldering, it becomes necessary to adapt solder to the electrodes on the sides of capacitors and this will also be disadvantageous for the downsizing of module size.
3) As shown in FIG. 1B, in a camera module, the solid-state image sensor is connected to the wiring portion (not shown) of the circuit board normally by the bonding wire 7. It is necessary to provide a space of 0.2 to 0.3 mm for this bonding wire and this will also become disadvantage for the downsizing of module size.
4) As shown in the camera module manufacturing process in FIG. 4, the solid-state image sensor is formed on the printed circuit board after the passive part 5 is formed by the reflow soldering and the lens holder 1 is formed after the wire bonding of the solid-state image sensor. If dust is attached on the surface of the solid-state sensor at this time, a defect that is called as a black flaw is produced in an image taken by this camera module. One pixel size of the solid-state image sensor 1 is normally 2 to 5 μm. To prevent this adhesion of dust, it is necessary to manufacture the camera module with a manufacturing line in a clean room and a large facility investment is required. Also, it becomes necessary to provide a cleaning equipment for removing dust adhered to the solid-state image sensor. The dust removing method is largely restricted for the reason that the surface of the solid-state image sensor is rough as there are micro-lenses 14 formed thereon and the material used is acrylic resist that is weak in mechanical strength.
5) As shown in FIG. 5, in the dicing process of the solid-state image sensor cutting from the wafer 11 after the semiconductor manufacturing process is completed, a semiconductor (normally, called as Si) is cut with a rotary grinding stone of an equipment that is normally called as a dicer. In this cutting work, however, a large amount of Si cutting waste is produced. These Si waste is washed away by washing water in the dicing process. However, the waste is partially get into the surface of the micro-lens and not removed in the succeeding washing process and thus generates the black flaw on the surface of the camera module. The final judgement of this black flaw is the step after the assembling of camera modules and all component parts (the solid-state image sensor, outer part 5, lens holder 1, optical lens 10, optical filter 8 and printed circuit board 2) accompanied to camera modules will be wasted.
6) Deviation of the mounting position of the lens holder 1 to the circuit board 2, flaw of the optical lens 10, defective optical characteristic, flaw and deviation of optical characteristic of optical filters, dust adhered to the lens holder, flaw, deviation of optical characteristic in the camera module manufacturing process are finally judged in the camera module test. Thus, if defects are determined at this stage, all component parts associated to the camera modules will be wasted.
Accordingly, it is an object of the present invention to provide camera modules that are small in size and easy to manufacture and to provide a manufacturing method thereof.